Valveless rotary displacement pump

ABSTRACT

A valveless rotary displacement pump comprising a cylindrical housing having inlet and outlet openings, a movable tubular membrane within said housing extending axially thereof with the forward edge of the membrane sealingly engaging the front wall of the housing, means sealing the membrane against the inner wall of the housing between the inlet and outlet openings, and a rotor mounted inside the membrane, said rotor pressing the membrane against the inner wall of the housing at substantially diametrically opposed axial lines, as the rotor rotates within the housing.

[ 1 Aug. 5, 1975 7/1972 Rosenberg.....................l 417/477 XFOREIGN PATENTS OR APPLICATIONS 551.541 ltaly......l. 417/477 ABSTRACT Avalveless rotary displacement pump comprising a 2 Drawing FiguresPrimary [;.\'u/mm'rC. Jr Husar Ass/stun! EmminerLeonard Smith Arm/7wAge/1! or FirmSalter 84 Michaelson cylindrical housing having inlet andoutlet openings a movable tubular membrane within said housing extendingaxially thereof with the forward edge of the membrane sealingly engagingthe front wall of the housing. means sealing the membrane against theinner wall of the housing between the inlet and outlet openings, and arotor mounted inside the membrane said rotor pressing the membraneagainst the inner wall of the housing at substantially diametricallyopposed axial lines, as the rotor rotates within the hous ing.

6 Claims.

VALVELESS ROTARY DISPLACEMENT PUMP Inventor: Otto Lutz, Bienroder Weg53, 33

Braunschweig. Germany Filed: July 17, 1973 Appl. No.1 379,929

Foreign Application Priority Data July 20 1972Germany....,...l.W.........v...

Field of Search References Cited UNITED STATES PATENTS 8/1950 5/195911/1968 McMillan...

United States Patent Lutz l l l VALVELESS ROTARY DISPLACEMENT PUMPBACKGROUND AND SUMMARY OF THE INVENTION The present invention concerns avalveless rotary displacement pump comprising a cylindrical housing anda movable membrane arranged within the interior of the housing andextending axially thereof so that the forward edge of the membrane makesa tight seal against the front wall of the housing. and means sealingthe membrane against the inner wall of the housing between the inletopening and the outlet opening of the pump, and a rotor mounted insidethe membrane pressing the membrane against the inner wall of the housingalong at least two rotating lines axial to the casing.

Known pumps of this type usually include a rotor with two pressurerollers which press a membrane against two rotating lines axial to thecasing by centrifugal forces or by the force of springs, in such a waythat two rotating delivery pockets are formed between the membrane andthe inner wall of the housing by means of which gases, liquids. orplastic solids-for instance, cement slurries-can be delivered from thesuction to the pressure side of the pump. ln known pumps, the suctionand pressure sides are separated from each other by means of a clampingdevice which holds a ledge formed in the membrane, or. in another case,the free ends of a membrane band which lie one upon another, stationaryand at the same time seals the suction side of the pump from thepressure side along this stationary line axial to the casing.

Although this pump is simple in its fundamental construction and itsmanufacture is relatively cheap, known pumps of this type have not, upto the present time, proved successful in practice, since it is onlypossible to operate them at low r.p.m.s, and, thus, only low deliverypowers can be achieved, The reason for this is that, especially at highr.p.m.s of the pump, the membrane is subjected to high peripheral forcesand tends to tear rapidly. Under these conditions, tearing occurschiefly in the region of the stationary clamping of the membrane by theknown clamping devices. These clamping devices have an additionaldisadvantage that when the pressure rollers of the rotor roll acrossthis position, the membrane is subjected to sharp bending at this point,which readily causes premature destruction of the membrane.

Another factor that makes prior art pumps of the above type notpractical where fast-running characteristics are desired is that, up tothe present, it has not proved possible to prevent vibration of themembrane, especially at high r.p.m.s.

The basic object of this invention is, therefore, to provide a pump ofthe type described above which can be operated at high r.p.m.s withcorrespondingly high powers of delivery and which has a sufficientlylong working life in normal operation.

This object is achieved, according to the present invention, byfabricating the membrane in the form of a tube with a constant Wallthickness which is braced against the smooth surface of the inner wallof the housing between the inlet opening and the outlet opening of thepump, by means of a sealing strip with a smooth surface,

A primary advantage of the pump according to the present inventionarises from the use of a membrane in the form of a tube. with noprojections or thickened extensions. in conjunction with the method ofbracing the membrane against the inner wall of the housing by the use ofsmooth surfaces, according to the invention. Bracing may occur along oneor more lines axial to the casing and can be produced by one or moresealing strips. in either case, according to the invention. sharpedgesclamps, which can easily cause damage to the membrane. are avoided.

it is advantageous that the sealing strip should press the membraneresiliently against the inner wall of the housing so that, on the onehand, the seal between the input opening and the output opening isinsured while. on the other hand, the membrane can slip or move in acircumferential direction. In this way it is possible for the membraneto partially compensate for the cxces sively high peripheral forces. Thefriction between the membrane and the inner wall of the housing is alsodecreased by this arrangement.

As a result of this invention, dangerous vibrations of the membrane,especially in fast-running pumps, are avoided since the membrane in theform of a tube is continuously maintained under tensile pre-stress bymeans of tensioning elements arranged within the membrane. in apreferred form of the invention. these tensioning elements are formed atthe sides of the seal ing strip in such a way that the transitionbetween the tensioning surfaces of the sealing strip and the tensioningelements at its side is rounded off.

An important feature of this invention is the fact that the tubularmembrane nowhere has a radius of curvature less than that imposed by thepressure rollers of the rotor. in this way, the working life ofthemembrane is prolonged, which is especially true when the radius ofcurvature of the rounding-off at the transistion between the tensioningsurface of the sealing strip and the tensioning elements at the side isthe same as that of the rollers of the rotor, and when the radius ofcurvature of this rounding-off and of the rollers is, respectively,greater than the least permissible bending radius of the membrane.

In a pump according to the present invention, the membrane consists of atube of metal or of a synthetic material which is resilient to bending.Special advantages occur when the membrane is of multilayerconstruction, Such membranes may, for instance, be manufactured from acoiled steel band or fabricated from two or more tubes of syntheticmaterial, for instance. which are pushed one inside the other. Membranesof multilayer construction, according to the invention, are capable ofwithstanding higher pressures in the delivery pockets of the pump andhave the additional advantage that the seal between the front edge ofthe membrane and the front wall of the pump housing is considerablyimproved. Owing to the multilayer construction of the membrane, a sealof a labyrinth type is produced in this position.

Another advantage of the present invention is that the interior of themembrane is connected to the highpressure side of the pump. As a resultof this, the membrane is better able to resist the pressure in thedelivery pockets.

In summary, 1 produce a pump, according to the present invention, whichcan be operated at relatively high r.p.m.s, and thus has relatively highpower of delivery, and whose membranes are long lasting in use. Thepumps can be economically produced, since they require neither closetolerances in manufacture nor expensive construction of bearings orhousing because of their practically complete mass balance.

Other objects, features and advantages of the invention will becomeapparent as the description thereof proceeds when considered inconnection with the accompanying illustrative drawings.

DESCRIPTION OF THE DRAWINGS In the drawing which illustrates the bestmode presently contemplated for carrying out the present invention:

FIG. I is a cross section through a pump according to the invention withthe rotor in a transverse position. and

FIG. 2 is a longitudinal section through the pump according to FIG. 1with the rotor in a vertical position.

DESCRIPTION OF THE INVENTION The valveless rotary displacement pump,according to the invention, as illustrated, consists essentially of thepump housing 3. the rotor 4, and the membrane 5.

The housing 3 is closed by a front cover 6 and has an inlet opening 7and an outlet opening 8 in the surface of its casing. The membrane ispressed, to provide a seal, against the inner wall of the housing alonga fixed line axial to the casing by means of a sealing strip 9,fabricated in two parts.

Pressure rollers 10 rotatably carried by the rotor 4 provide rotatingaxial lines along which a seal is made between the membrane 5 and theinner wall of the housing 3. The axial sealing lines, the inner wa l ofthe housing 3, and the membrane 5 define delivery pocket ll, as can bemost clearly seen in FIG. 1. PK]. 1 repre sents one extreme position ofthe rotor 4. in this position the delivery pocket 11 is sealed off fromthe inlet and outlet openings 7 and 8 and has the maximum suction volumewhich will be sucked in twice during each rotation of rotor 4. Thedelivery capacity of the pump, as illustrated, can, however, be furtherincreased if the rotor axle 12 is mounted not, as illustrated, on thecentral axis of the cylindrical housing 3, but somewhat above thisposition. The suction volume of the pump will be increased by such anarrangement.

Another extreme position of the rotor is attained when the latter hasreached the position shown in FIG. 2. In this position, the fixed axialsealing line is coinci dent with one of the rotating axial sealing linesso that the membrane is pressed against the inner wall of the housing 3to form a seal at two positions only. The advantage of providing thetwo-part sealing strip 9, according to the invention, with tensioningelements 13 at the sides, is particularly apparent at this position ofthe rotor. The membrane 5 bears against a mounting support and is thusheld continuously under a tensile pre-stress, so that any vibration ofthe membrane 5 is eliminated.

ln particular, it can be seen from FIG. 1 that the sealing strip 9,which is attached to the front wall 6 of the housing by means ofatension anchor 14, has a smooth surfaced tensioning face 15, which isessentially parallel to the curved inner wall of the housing 3. Thetransitions from the tension face 15 of the sealing strip 9 to thetensioning elements 13 at the side is provided with rounded-off portions16, which, in a preferred form of the invention, have a radius ofcurvature equal to the radius of curvature of the rollers 10. In thisway the flexible membrane 5 is not subjected at any point to bending toa larger extent than is permissible. The membrane 5 can slip or slidebetween the tensioning face 15 and the inner wall of the housing 3without breaking the seal between the suction side and the pres' sureside of the pump, so that the membrane is not subjected to excessiveperipheral forces arising from the rotation of the rotor 4.

The membrane 5 is flexible and bendable but has no extensibility in acircumferential direction. it may be fabricated as an endless tube frommetal or synthetic material, for example, snythetic materialstrengthened with glass fiber, and can be easily replaced in the pumpaccording to the invention as it only needs to be pushed over the rotor4 and the sealing strip 9 in the pump housing 3. An especially good sealbetween the forward edge of the membrane 5 and the front wall of thehousing 3for example, the housing cover 6is produced when multiple-layermembranes are employed.

The rotor 4 of the pump according to the invention is fixedly mounted onthe rotor axle 12 by means of a pin 17. The rotor axle 12 is mounted inthe front wall of the housing 3 in roller bearings l8. It is obviouslypossible to use other types of bearings if desired. Rollers 10 arefixedly mounted in needle bearings 20 at the side ends of the transversecarrier 19 of the rotor 4. These needle bearings 20 may also be replacedby bearings of other types-for instance, slide bearings, carbon bearingsor the like. In this way, the roller surfaces of the rollers 10 arefixed at a distance from the inner wall of the housing 3 whichcorresponds with the thickness of the membrane 5. It would be possibleto mount the rollers 10 in bearings on the transverse carrier 19 of therotor 4 so as to be movable in such a way that they are urged againstthe inner wall of the housing 3 by centrifugal forces or by the force ofsprings (not shown). However, the rollers 10 may also be advantageouslymounted in fixed bearings on the transverse carrier l9 of the rotor 4.By correct adjustment of the rollers relative to the inner wall of thehousing, the friction between the membrane and the inner wall of thehousing can be considerably lessened so that the working life of themembrane is once again increased.

As further shown in FIG. 1, the interior of the membrane 5 is connectedto the high pressure side of the pump through a passage 22 that extendsthrough one of the end walls of the pump, whereby a pressure balancebetween the interior of the membrane and the pressure outlet 8 is alwaysmaintained.

While there is shown and described herein certain specific structureembodying the invention, it will be manifest to those skilled in the artthat various modifications and rearrangements of the parts may be madewithout departing from the spirit and scope of the unde rlying inventiveconcept and that the same is not lim ited to the particular forms hereinshown and described except insofar as indicated by the scope of theappended claims.

What is claimed is:

l. A valveless rotary displacement pump, comprising a housing formedwith an interior chamber defined by an inner cylindrical wall andrelatively flat end walls, inlet and outlet openings formed therein insaid cylindrical wall in angular spaced apart relation, a movablemembrane located in said housing having a tubular configuration andhaving a constant wall thickness, the longitudinal axis of said membranebeing parallel to the longitudinal axis of said chamber, wherein theedges at both ends of the membrane sealingly engage the end walls ofsaid chamber, the outer surfaces of said mem brane sealingly engagingthe cylindrical inner wall of the chamber between the inlet and outletopenings thereof. a rotor rotatably mounted in said housing and locatedwithin the interior of the membrane. transversely spaced roller meansmounted on said rotor for continuously engaging the interior surfaces ofsaid membrane for urging the membrane against the cylindrical wall ofthe chamber along at least two rotating lines that are located inparallel relation to the axis of said cylindrical chamber, said sealingelements being secured to said end walls and engaging the inner surfaceof said membrane with a smooth surface for urging the membrane againstthe inner wall of the chamber between the inlet and outlet openingsthereof to effect a seal between said openings, and allowing freecircumferential movement of said membrane between the inner wall of saidchamber and surfaces of said sealing elements.

2. A pump as claimed in claim l, the interior of said membranecommunicating with the pressure side of said pump.

3. A pump as claimed in claim 1, said sealing element including tensionelements that are joined thereto. said tension elements having roundedsurfaces that engage the inner surface of said membrane for tensioningsaid membrane during rotation of said rotor and rollers mounted thereon.

4. A pump as claimed in claim 3, said tensioning elements being locatedat each circumferential end of said sealing element and the surface ofsaid sealing element with which said membrane engages being rounded atsaid ends.

5. A pump as claimed in claim 4, a carrier mounted on said roller andextending transversely with respect thereto, said rollers being mountedon said carrier on opposite ends thereof.

6. A pump as claimed in claim 5, the radii of curvature of the roundedportions of the surfaces of said sealing element at its ends and tensionelements that en' gage said membrane being substantially equal to theradii of curvature of the rollers of the rotor.

1. A valveless rotary displacement pump, comprising a housing formedwith an interior chamber defined by an inner cylindrical wall andrelatively flat end walls, inlet and outlet openings formed therein insaid cylindrical wall in angular spaced apart relation, a movablemembrane located in said housing having a tubular configuration andhaving a constant wall thickness, the longitudinal axis of said membranebeing parallel to the longitudinal axis of said chamber, wherein theedges at both ends of the membrane sealingly engage the end walls ofsaid chamber, the outer surfaces of said membrane sealingly engaging thecylindrical inner wall of the chamber between the inlet and outletopenings thereof, a rotor rotatably mounted in said housing and locatedwithin the interior of the membrane, transversely spaced roller meansmounted on said rotor for continuously engaging the interior surfaces ofsaid membrane for urging the membrane against the cylindrical wall ofthe chamber along at least two rotating lines that are located inparallel relation to the axis of said cylindrical chamber, said sealingelements being secured to said end walls and engaging the inner surfaceof said membrane with a smooth surface for urging the membrane againstthe inner wall of the chamber between the inlet and outlet openingsthereof to effect a seal between said openings, and allowing freecircumferential movement of said membrane between the inner wall of saidchamber and surfaces of said sealing elements.
 2. A pump as claimed inclaim 1, the interior of said membrane communicating with the pressureside of said pump.
 3. A pump as claimed in claim 1, said sealing elementincluding tension elements that are joined thereto, said tensionelements having rounded surfaces that engagE the inner surface of saidmembrane for tensioning said membrane during rotation of said rotor androllers mounted thereon.
 4. A pump as claimed in claim 3, saidtensioning elements being located at each circumferential end of saidsealing element and the surface of said sealing element with which saidmembrane engages being rounded at said ends.
 5. A pump as claimed inclaim 4, a carrier mounted on said roller and extending transverselywith respect thereto, said rollers being mounted on said carrier onopposite ends thereof.
 6. A pump as claimed in claim 5, the radii ofcurvature of the rounded portions of the surfaces of said sealingelement at its ends and tension elements that engage said membrane beingsubstantially equal to the radii of curvature of the rollers of therotor.